This invention relates to the art of die forming workpieces and, more particularly, to an improved tool assembly for maintaining alignment between a tool and die during the shaping of a workpiece therebetween.
The present invention finds particular utility in connection with the shaping of air gun pellets form a spherical lead workpiece and, accordingly, will be described in detail hereinafter in connection with such use. However, it will be appreciated that the invention can be used in connection with the production of other products and in connection with the die forming of products from workpieces other than lead.
It is of course well known that air gun pellets have an hourglass shape and are formed by inserting a lead workpiece of specific weight into the cavity of a split die and shaping the workpiece therein through the use of a punch. The punch is axially reciprocated relative to the die cavity and, following the forming operation, the split die opens, the punch is withdrawn and the pellet stripped therefrom. The dies are then closed, a new workpiece is introduced between the punch and die, and the forming procedure is repeated.
A number of problems are encountered in connection with high speed production of such pellets including, for example, excessive wear of relatively moving parts of the tool assembly. Such wear results from extrememly close tolerances between the relatively moving parts and the difficulty in maintaining alignment between relative displaceable parts which move into and out of engagement with one another, such as the working end of the punch and die cavity in which the workpiece is shaped. Such alignment problems impose side thrust loads on the parts which in addition to promoting wear, can result in damage to the parts. Additionally, these problems render it difficult to consistently produce acceptable end products, and to produce products at an acceptable parts per minute production rate without excessive down-time for maintenance and/or replacement operations. Additionally, the provision of close tolerances between relatively moving component parts undesirably adds to the initial manufacturing cost as well as maintenance and replacement cost in connection with the tooling.
So called "floating" tooling has of course been provided heretofore in which, in the case of a punch for example, the tool is so mounted that the working end can deflect into alignment with a die cavity or the like in which the forming work is performed. However, such self-alignment often requires engagement of the working end of the tool with a guide surface or the like which enables achieving alignment of the die and tool axes as the tool moves into the die. Such engagement between the tool and guide surface is undesirable for a number of reasons including, in connection with high speed tool movement, excessive wear and potential damage to the tool. Moreover, if such alignment is not achieved before the forming process begins, such self-aligning desplacement of the tool can result in the forming of an unacceptable product. This is especially true in connection with the forming of air gun pellets, both because of the size thereof and the material from which they are formed. Moreover, these problems are compounded as a result of high speed reciprocating displacement of the tool necessary to achieve a desired high production rate.
Tooling damage and the production of unacceptable workpieces have also been encountered heretofore, especially in connection with efforts to attain high speed production, as a result of the misfeeding of workpieces during the working cycle. In particular, the feeding of more than one workpiece into the tooling assembly, or the partial feeding of a workpiece thereinto, can result in jamming in the tool assembly and/or bending of the punch. Moreover, such misfeeding can result in damage to the parts of the assembly which the punch and workpiece are moving relative to. Even if such misfed workpiece material reaches the die, the excess or inadequacy of the amount of material results in an unacceptable product.